She says the 6-month old Rottweiler mix wagged his way into her heart pretty quickly.

"He kind of gallops around and jumps up," Peart says.

It is pretty amazing for a guy who had heart surgery, 3 days ago.

"I honestly can't tell a difference in him at all," Peart says. "He's still the same happy puppy."

Mason landed here the busy metro Atlanta shelter when he was just a few months old. He was picked up by DeKalb Animal Control. Peart says an officer found him tied up outside without access to food or water. When a shelter vet examined him there was a problem.

"She could feel some vibration in his chest, which usually signifies a pretty severe heart murmur," Peart says.

The news got worse. Tests revealed Mason didn't just have a murmur, he had a very rare, complicated condition known as sub-aortic stenosis, which was causing his heart to work much harder than it should.

"It was going to be a 10,000 to 15,000 surgery," Peart says.

So the rescue coordinator started calling veterinarians, with no luck. Then she found The Auburn University School of Veterinary Medicine's Dr. Daniel Newhard, a cardiology surgeon. Newhard and his team agreed to try to help Mason. The school says a donor paid for the dog's surgery. For Andie Peart, it was a major breakthrough.

"I had been fostering him at my house, so I'm very much in love with him. So, when they agreed to do that, I was just extremely, extremely beside myself."

Newhard says used a balloon-tipped catheter to reopen Mason's blockage. After the dog was placed under general anesthesia, Newhard's team threaded the catheter through Mason's jugular vein.

"We put the catheter into his heart, and the balloon up into the affected valve, and inflated it with a lot of strength," Dr. Newhard says. 'That kind of popped that open. We did that two times."

The procedure worked; Mason's heart pressures dropped by half.

"It means that he is going to get a chance at life that he wouldn't have had," Andie Peart says.

The day after his surgery, a volunteer brought Mason back to the shelter.

"I carried him around for a while, so he could say hi to everybody," Peart says.

Three days later, Sarah Rosenblum, the founder and executive director of Bullpen Rescue in Norwood, Georgia, came to meet Mason.

"He's even dreamier in person," Rosenblum laughs.

Bullpen Rescue helps large-breed dogs, and special cases.

"Dogs like Mason," Rosenblum says. "Dogs that most rescues just look at and say, 'It's just too much to take on."

Mason will have to rest for 8 weeks, to allow his heart time to heal. But, Rosenblum has already lined up a medical foster home for him. And, when he's healed, she's certain she'll have no trouble finding an adopter.

"I am perpetually amazed by the goodness of humans when it comes to opening their hearts and their lives with these dogs," she says.

And Andie Peart says her heart, too, is full, with gratitude for the people who saved the Rottie puppy with a broken heart.

"It takes a village really, to make something like this happen," she says. "And that's what LifeLine is all about. We're going to do whatever we can to save as many lives as possible."

To read more about Bullpen Rescue, visit www.bullpenrescue.org.

If you would like to help a rescue animal, LifeLine Animal Project says its DeKalb and Fulton shelters have together taken in 1,500 dogs and cats in the past month.

Fulton Animal Services is full, and they are waiving adoption fees through the end of July.